Detective Inspector Paul Hughes, who is in charge of the investigation, said: "In July 2018 a healthcare professional was arrested on suspicion of murder in relation to the deaths of eight babies and the attempted murder of six babies at the neonatal unit at The Countess of Chester Hospital.

"She was subsequently bailed pending further inquiries.

"As part of our ongoing investigation we have re-arrested the healthcare professional on suspicion of murder in relation to the deaths of eight babies and the attempted murder of six babies.

"She has also been arrested in connection with the attempted murder of three additional babies.

Lucy Letby qualified as a Children's Nurse from The University of Chester in 2011. Picture: Facebook

"The woman is currently in custody helping officers with their inquiries."

Her arrest came after concerns were raised about a "higher than usual number of neonatal deaths" in June 2015.

Cheshire Constabulary launched its investigation two years ago, with detectives working on the "highly complex and very sensitive case" since.

At the time of her arrest, one friend of the Letby's described Lucy as a "professional nurse" who was dedicated to her "dream job" and "wouldn't hurt a fly".

Lucy Letby. A neighbour said: “She was as sweet as anything.” Picture: Facebook

The woman, who wished to remain anonymous, said: "Lucy was doing the job she dreamt of doing and appeared nothing but dedicated and professional.

"You can't imagine her hurting a fly let alone defenceless babies."

A neighbour added: "I knew her when she was a little girl and she was as sweet as anything. I've seen her grow up and she seemed a lovely woman.

"So this news is deeply and utterly shocking. I can't fathom it."

The scope of the investigation has been widened to 17 baby deaths and 16 non-fatal collapses between March 2015 and July 2016.

Susan Gilby, chief executive of the Countess of Chester NHS Foundation Trust, said: "Our thoughts are with the bereaved families. We are co-operating fully with the ongoing police investigation and so are unable to comment further at this time."

Det Insp Hughes added: "I would like to reassure people that we are doing everything we can as quickly as we can to identify what has led to these baby deaths and collapses.

"Due to the nature of this investigation it is extremely challenging but it is important to remember that it is very much active and ongoing - there are no set timescales and we remain committed to carrying out a thorough investigation as soon as possible.

"We fully appreciate that it continues to have a big impact on all those involved - including the families of the babies, staff and patients at the hospital as well as members of the public.

"Parents of all the babies are continuing to be kept fully updated and are being supported throughout the process by specially trained officers. This is an extremely difficult time for all the families and it is important to remember that, at the heart of this, there are a number of bereaved families seeking answers as to what happened to their children.

"At this stage, we are unable to go into any further details about the investigation but as soon as we can provide any further updates we will do."

This article was originally published in The Sun and is reprinted here with permission.